1. Field of the Invention
The invention relates to the field of separation systems for missile launch vehicle payload fairings and the like and, in particular, to a separation system that reduces shock loads in the missile and payload.
2. Description of Related Art
The typical systems for mechanically securing segments of a payload fairing together use explosively actuated fasteners, such as explosive bolts and the like. Another type of explosive actuated system uses a metal coupling to join the segments of the fairing together. A tubular member is positioned next to or within the coupling. Upon ignition, the explosive expands the tubular member, which in turn fractures the coupling. Such a system is disclosed in U.S. Pat. No. 5,443,492 xe2x80x9cPayload Housing And Assembly Joint For A Launch Vehiclexe2x80x9d by A. L. Chan, et al.
However, pyrotechnic fasteners and the like, while well proven, can not be tested prior to use, thus must be assembled with great care. This makes them generally expensive to manufacture. Special storage areas must be set aside for any device containing explosives. They are always subject to inadvertent actuation, and, therefore, handled with great care. Additionally, they are particularly subject to ignition by electromagnetic interference (EMI) and thus must be protected by EMI shielding devices, which also raises the cost. Another disadvantage is that, due to the fact that the explosive charge can be ignited by exposure to high temperature, they have a limited environmental temperature range. One of the most important disadvantages is that upon actuation, most generate significant shock loads, which can damage nearby equipment.
Thus in order to eliminate the above disadvantages non-pyrotechnic designs have emerged. For example, U.S. Pat. No. 5,046,426 xe2x80x9cSequential Structural Separation Systemxe2x80x9d by G. J. Julien, et al. uses a sequence of wires or foil strips attached by their ends to the edges of adjoining segments, thus securing them together. But when heated the wires or foils melt allowing the segments to separate. By varying the lengths of the wires or foils in sequence, they can be made to fuse in sequence. The disadvantage of this system is that every wire or foil must be separately connected to an electrical circuit. This adds complexity.
Thus, it is a primary object of the invention to provide a system for securing the segments of a structure together and to provide for separation of the segments.
It is another primary object of the invention to provide a system for securing the segments of a structure together and to provide for the separation of the segments in a sequential manner.
It is a further object of the invention to provide a system for securing the segments of a structure together and to provide for separation of the segments without significant shock loads being introduced into the structure.
The invention is a separation system for releasably securing first and second structural members together. In detail, the invention includes at least one first pulley mounted on the first structural member and at least one-second pulley mounted on the second structural member. A cable is attached by one end to the first structural member and wound about the first and second pulleys and is attached by its second end to the second structural member. Preferably there are two or more first and second pulleys with the cable alternately wound between said first and second pulleys with one end of cable attached to the first structural member and the opposite end attached to the second structural member. Thus the cable holds the first and second structural members together. A system to sever the cable is included, which upon actuation will allow the two structural members to separate. Preferably the system to sever the cable is an explosively actuated cable cutter. In addition, a retaining device is provided for securing the cable to one of the pulleys such that upon severing thereof, the cable is secured to the fairing half.
The cable is preferably made of a low melting point high strength material such as a liquid crystal thermotropic (melt spun) polyester polyarylate fiber such as VECTRAN(copyright) manufactured by Hoechst Celanese, Charlotte, N.C., or a lyotropic (solvent spun) aromatic polyaramide fiber, such as KEVLAR(copyright), manufactured by E. I. duPont de Nemours and Company, Delaware.
The system to sever the cable can also include at least one heating device in contact with the cable and coupled to an electrical power supply. The at least one heating device includes an arm having first and second ends, with the first end pivotally attached to one of the structural members in proximity to the cable. A heating element is mounted on the second end of the arm. A spring is used to urge the arm toward the cable such that the heating element is in contact with the cable. Thus upon actuation, the heating element xe2x80x9cmeltsxe2x80x9d through the cable allowing the fairing halves to separate.
The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description in connection with the accompanying drawings in which the presently preferred embodiments of the invention are illustrated by way of examples. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and are not intended as a definition of the limits of the invention.